Ask HN: Using QR code to track my Expenses?

I have seen many people interested in tracking their daily expenses and knowing how much they spend on their food, clothing, rent, alcohol, etc. Some use excel sheets and some use specialized software, but biggest hindrance is manually entering expenses and categorizing it which is time consuming and hence, less effective (even bank transactions don't give individual item information).

I was wondering if it is possible to use QR code printed on the back side (or somewhere else?) of the bill/receipt by stores which will summarize the expenses and I just use my smartphone to automatically scan and save the details for my future analysis.

Do you think the limit on amount of data stored by QR code could be a problem? Any suggestions on how this problem can be tackled (using multiple QR codes/ colored QR codes)? Also, do you think dependency on the stores to print QR code summarizing the bill/receipt would be a big hurdle?

Appreciate your views/suggestions.